The present invention relates to a carbonaceous cylindrical body of a small caliber, of which the bulk density, the gas permeability, the thermal conductivity and the thickness can be adjusted in the respective favorable ranges, and to a process for producing the carbonaceous cylindrical body.
More in detail, the present invention relates to a carbonaceous cylindrical body comprising a composite body consisting of a carbonized material of a thin paper-like supporting body which has been prepared by manufacturing a paper-like body so that its carbonizable fibers are oriented and shows the strength ratio of the lengthwise direction to the widthwise direction of from 2 to 10 and a carbonaceous matrix showing an optically isotropic structure or an optically anisotropic structure having mosaic structure consisting of particles of not more than 10 .mu.m in size under a polarizing microscope, the carbonaceous cylindrical body showing a carbon content of not less than 85% by weight, an oxygen gas permeation coefficient of from 10.sup.-2 to 10.sup.-7 cm.sup.2 /sec. Under a partial pressure of oxygen of 1 atm and a bulk density of from 1.4 to 1.9 g/cm.sup.3, and also relates to a process for producing the carbonaceous cylindrical body showing an carbon content of not less than 85% by weight, an oxygen gas permeation coefficient of from 10.sup.-2 to 10.sup.-7 cm.sup.2 /sec. Under a partial pressure of oxygen of 1 atm and the bulk density of from 1.4 to 1.9 g/cm.sup.3, the process comprising the steps of (1) providing a carbonizable precursor of carbon onto a thin paper-like supporting body which has been obtained by manufacturing a paper-like body so that its carbonizable fibers are oriented and shows the strength ratio of the lengthwise direction to the widthwise direction of from 2 to 10, thereby obtaining a carrying body, (2) hardening said carrying body by heating thereof singly under pressure, thereby obtaining a sheet-like molded material or (2') after laminating a number of said carrying bodies so that the respective directions of orientation of said fibers are the same, hardening and thus laminated carrying bodies by heating under a pressure, thereby obtaining a sheet-like molded material, (3) winding cylindrically said sheet-like molded material in the lengthwise direction in a single layer or in multiple layers, thereby forming a cylinder-form material and (4) carbonizing said cylinder-form material at a temperature of not lower than 800.degree. C. in an inert atmosphere.
Since the carbonaceous cylindrical body having a single layer structure or multiple layers structure of the present invention has heat-resistance and corrosion-resistance which are characteristic to carbon materials, and the gas permeation coefficient can be adjusted over a wide range, it is useful in the various uses requiring electroconductivity, thermal conductivity and the gas-impermeability at the same time of requiring the heat-resistance and corrosion-resistance.
As a carbonaceous thin plate and a process for producing the same, the following have been proposed.
Japanese patent application Laid-Open (KOKAI) No. 59-26907 (1984) discloses a thin plate of graphite produced by a process comprising the steps of preparing a paste by adding a liquid thermosetting resin to a micro-powdery graphite which is not more than 100 .mu.m in size and has been thermally treated preliminarily to a temperature of not lower than 2700.degree. C. and kneading the thus formed material, molding the thus obtained paste into a thin-plate form by a rolling molder, hardening the thus obtained thin plate by heating thereof or hardening the thin plate while placing the heating plates on the both side of the thin plate under a pressure and then carbonizing the thus hardened thin plate by heating thereof, and the process for producing the thin plate of graphite.
Japanese patent application Laid-Open (KOKAI) No. 59-21514 (1984) discloses a process for producing a glass-like thin plate of carbon, which process comprises the steps of mixing a chlorinated resin of vinyl chloride and/or a vinyl chloride resin with a furan resin, kneading the thus obtained mixture, molding the thus kneaded mixture into a film or a sheet, subjecting the thus obtained, molded material to a treatment to form a carbon precursor and calcining the carbon precursor in an inert atmosphere.
Although the carbonaceous thin plates and the processes for producing thereof have been proposed in large numbers as shown above, the carbonaceous cylindrical body obtained by carbonizing and calcining the cylindrical body prepared by winding cylindrically the molded body of the carbonaceous thin plate into a small caliber while utilizing the flexibility thereof cannot be put to practical uses because of the large occurrence of crevices and cracks. Moreover, it is also difficult to obtain a thin carbonaceous cylindrical body excellent in dimensional accuracy.
On the other hand, a process for producing a cylinder with a thin wall, which comprises the steps of (1) mixing a pitch obtained by thermally treating a petroleum tar or a coal tar as a binder, with coke, (2) kneading the thus obtained mixture into a paste, (3) extruding the thus obtained paste into a cylindrical form by an extruder, (4) repeating the calcination thereof and the impregnation of the above-mentioned pitch thereinto, thereby compacting the material of the cylinder and (5) subjecting the thus obtained cylinder to machining, has been generally carried out. However, the above-mentioned process requires complicated steps such as machining and accordingly, the process is disadvantageous economically.
Moreover, a carbonaceous thin plate comprising a composite body consisting of a thin paper-like supporting body which has been used as the base material and has been substantially carbonized and a carbonaceous matrix showing an optically isotropic structure or an optically anisotropic structure having mosaic structure consisting of particles of not more than 10 .mu.m in size under a polarizing microscope and showing a carbon content of not less than 95% by weight, a gas-permeation coefficient of from 10.sup.-5 to 10.sup.-7 cm.sup.2 /sec, a specific resistance of from 2.times.10.sup.-3 to 6.times.10.sup.-3 .OMEGA..cm in the direction of thickness, a bulk density of from 1.4 to 1.9 g/cm.sup.3 and the process for producing thereof have been also disclosed (refer to Japanese patent application Laid-Open (KOKAI) No. 60-239358 (1985)).
Although the above-mentioned patent application offers a thin plate in which crevices and cracks do not occur, particularly in the case of producing a cylindrical body of a small caliber while utilizing the flexibility of the thin carrying body prepared by the steps of impregnating the carbonizable precursor material into a thin paper-like supporting body which has been substantially carbonized and hardening the thus treated supporting body by heating under pressure, it has been impossible to avoid the occurrence of crevices and cracks when the cylindrical body is formed.
As a result of the present inventors' earnest researches for solving the above-mentioned problem and finding a process for producing a carbonaceous cylindrical body excellent in dimensional accuracy and with a thin wall, in which crevices and cracks scarcely occur even in the case of the small caliber thereof, without taking complicated steps and in a low producing cost, it has been found out by the present inventors that in the case where a carbonizable precursor of carbon is provided onto a thin paper-like supporting body, which has been obtained by manufacturing a paper-like body so that its carbonizable fibers are oriented and shows the strength ratio of the lengthwise direction to the widthwise direction of from 2 to 10, to obtain a carrying body, and thus obtained carrying body is hardened singly by heating thereof under pressure or a multiple number of the carrying bodies are laminated in the same direction and are hardened by heating thereof under pressure, the thus obtained sheet-like molded material is wound cylindrically in the lengthwise direction in a single layer or in a multiple layers to form a cylindrical body and the thus formed cylindrical body is carbonized and calcined, the cylindrical body wound in the lengthwise direction is tough due to the reinforcing effect formed by the lengthwise orientation of the fibers in the paper-like supporting body, crevices and cracks scarcely occur in the steps of carbonization and calcination even in the case of a small caliber and a carbonaceous cylindrical body excellent in the dimensional accuracy can be produced in a simple process, and on the basis of the above-mentioned finding, the present inventors have attained the present invention.